This invention relates in general to rotatable drive connections, such as are commonly used with flexible driveshafts for transmitting rotational power from a driving component to a driven component. In particular, this invention relates to an improved structure for such a rotatable drive connection that reduces chatter and that is cost effective to manufacture and assemble.
Flexible driveshafts are used in a wide variety of applications including vehicles, surgical apparatuses, robotics, machine tools, and the like. For example, flexible driveshafts are commonly used in power vehicle seat assemblies for transmitting rotational power from a bi-directional motor to a gear box. The gear box typically includes a lead screw having a drive nut threaded thereon for converting rotational movement of the lead screw into linear movement of the drive nut. The drive nut is attached to the seat assembly for effecting linear movement thereof whenever the motor is operated. In such an application, a flexible driveshaft can be routed along a non-linear path or can be maneuvered over, under, or around obstacles between the motor and the gear box. Thus, the flexible driveshaft provides for numerous possibilities in positioning a driving component and driven component relative to one another.
Flexible driveshafts of this general type are typically provided with end portions having non-circular cross sectional shapes. These non-circular end portions can be inserted into corresponding hollow sockets provided on the driving and driven components to provide rotatable driven, axially movable connections. It is known to provide both the end portion of the flexible driveshaft and its corresponding hollow socket with square cross sectional shapes for these purposes.
However, because the hollow socket is typically larger in size than the end portion of the flexible driveshaft (either by design or as a result of manufacturing tolerances), there can be looseness therebetween. Such looseness may generate undesirable noise and vibration as the flexible driveshaft is rotated, which is commonly referred to as chatter. A number of structures have been developed for reducing such chatter. For example, a coating or clip can be applied onto the end portion of the flexible driveshaft for taking up some of the looseness. It is also known to provide a twist or helix along the end portion that is disposed within the hollow socket. However, these and other known structures can undesirably increase manufacturing and assembly costs. Thus, it would be desirable to provide an improved rotatable drive connection that both reduces chatter and is simple and inexpensive to manufacture and assemble.